hi Folks,
I've made a simple voltage divider to bring 350VDC down to a max of 3.3 for measuring. I've done this with 3 470k resistors (0.6W) and a 10K to ground. Across the 10K I also have a 3.3 zener in the (vain?) hopes that should something happen to one of the 470s, it would clamp the voltage.
I've built this on vero board and removed the tracks (heat, soften glue, rip off) between the resistors (two tracks spacing).
Is there anything else I should be doing to remain / keep my netduino save? Resistors are rated at 250V each.
Should I have something the other way round? i.e. if the 10k resistor goes open (can it happen?) I still see the zener taking the brunt if that happens?
Would the power dissapated by the zener be (Vin - 3.3) * I or V*I? it's only only a 1/4W. The way I see it is if one of the 470s shorts, I will have a Vin of over 5V @7uA which is still very low.
questions questions questions
TIA
Cheers,
Crispin
I've made a simple voltage divider to bring 350VDC down to a max of 3.3 for measuring. I've done this with 3 470k resistors (0.6W) and a 10K to ground. Across the 10K I also have a 3.3 zener in the (vain?) hopes that should something happen to one of the 470s, it would clamp the voltage.
I've built this on vero board and removed the tracks (heat, soften glue, rip off) between the resistors (two tracks spacing).
Is there anything else I should be doing to remain / keep my netduino save? Resistors are rated at 250V each.
Should I have something the other way round? i.e. if the 10k resistor goes open (can it happen?) I still see the zener taking the brunt if that happens?
Would the power dissapated by the zener be (Vin - 3.3) * I or V*I? it's only only a 1/4W. The way I see it is if one of the 470s shorts, I will have a Vin of over 5V @7uA which is still very low.
questions questions questions
TIA
Cheers,
Crispin